Method for downlink channel reception in wireless communication system and device therefor

ABSTRACT

The present invention provides a method for downlink channel reception by a terminal in a wireless communication system and a device therefor. Specifically, a method for downlink channel reception by a terminal in a wireless communication system may comprise the steps of: receiving, from a base station, beam configuration information relating to a plurality of transmission beams of the base station; receiving, from the base station, beam indication information indicating one or more transmission beams among the plurality of transmission beams of the base station; and receiving a downlink control channel through a specific transmission beam among the one or more transmission beams, on the basis of the received beam configuration information and the received beam indication information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/403,418, filed on May 3, 2019, which is a continuation ofInternational Application No. PCT/KR2017/009463, filed on Aug. 30, 2017,which claims the benefit of U.S. Provisional Application No. 62/417,324,filed on Nov. 4, 2016, the contents of which are all hereby incorporatedby reference herein their entireties.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method of receiving, by a terminal, a downlinkchannel from a base station in a wireless communication system and adevice supporting the same.

BACKGROUND ART

Mobile communication systems have been generally developed to providevoice services while guaranteeing user mobility. Such mobilecommunication systems have gradually expanded their coverage from voiceservices through data services up to high-speed data services. However,as current mobile communication systems suffer resource shortages andusers demand even higher-speed services, development of more advancedmobile communication systems is needed.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive multiple input multipleoutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

The present invention proposes a method of receiving a downlink channelby a terminal in a wireless communication system.

Specifically, the present invention proposes a method of transmitting,by a base station, information indicating a transmission beam to aterminal in order to perform a beam scanning operation between theterminal and the base station.

To this end, the present invention proposes a method using a preamble ora specific physical channel as information indicating a transmissionbeam.

Furthermore, the present invention proposes a method of grouping thetransmission beams of a base station into a plurality of beam sets ifthe number of transmission beams to be indicated is many and allocatinga specific resource region to each beam set.

Technical objects to be achieved in the present invention are notlimited to the above-described technical objects, and other technicalobjects not described above may be evidently understood by a personhaving ordinary skill in the art to which the present invention pertainsfrom the following description.

Technical Solution

In an embodiment of the present invention, a method of receiving, by aterminal, a downlink channel in a wireless communication system includesreceiving, from a base station, beam configuration information for aplurality of transmission beams of the base station, receiving, from thebase station, beam indication information indicating at least one of theplurality of transmission beams of the base station, and receiving adownlink control channel through a specific transmission beam of the atleast one transmission beam, based on the received beam configurationinformation and the received beam indication information. The beamconfiguration information includes configuration information indicatingone or more beam sets for the plurality of transmission beams.

Furthermore, in the method according to an embodiment of the presentinvention, the one or more beam sets may be configured in differentresource regions in which the downlink control channel is capable ofbeing transmitted.

Furthermore, in the method according to an embodiment of the presentinvention, at least one of a time resource or a frequency resource maybe configured differently for each resource region configured for theone or more beam sets.

Furthermore, in the method according to an embodiment of the presentinvention, the specific transmission beam may be indicated through aspecific preamble or a specific physical channel received in a symbolprior to a symbol in which the downlink control channel is received.

Furthermore, the method according to an embodiment of the presentinvention may further include reporting, to the base station,information for one or more transmission beams of the plurality oftransmission beams by performing beam measurement on the plurality oftransmission beams of the base station.

Furthermore, in the method according to an embodiment of the presentinvention, the information for the one or more transmission beams mayfurther include information for one or more reception beams of theterminal corresponding to the one or more transmission beams.

Furthermore, in the method according to an embodiment of the presentinvention, the beam configuration information and the beam indicationinformation may be received through higher layer signaling.

Furthermore, in the method according to an embodiment of the presentinvention, the beam configuration information may be received through aradio resource control message, and the beam indication information maybe received through a medium access control (MAC) control element (CE).

Furthermore, in the method according to an embodiment of the presentinvention, the beam configuration information may be received throughhigher layer signaling, and the beam indication information may bereceived through downlink control information.

Furthermore, in the method according to an embodiment of the presentinvention, the size of the one or more beam sets may be determined basedon a time unit in which downlink control information of the specificphysical channel is capable of being transmitted.

Furthermore, in the method according to an embodiment of the presentinvention, the scheduling of the resource region configured in each ofthe one or more beam sets may be performed in a specific resource blockunit.

Furthermore, a terminal receiving a downlink channel in a wirelesscommunication system according to an embodiment of the present inventionincludes a transceiver configured to transmit and receive radio signalsand a processor functionally connected to the transceiver. The processormay be configured to receive, from a base station, beam configurationinformation for a plurality of transmission beams of the base station,receive, from the base station, beam indication information indicatingat least one of the plurality of transmission beams of the base station,and receive a downlink control channel through a specific transmissionbeam of the at least one transmission beam, based on the received beamconfiguration information and the received beam indication information.The beam configuration information may include configuration informationindicating one or more beam sets for the plurality of transmissionbeams.

Advantageous Effects

In accordance with an embodiment of the present invention, atransmission and reception operation on a signal and/or a channel can beefficiently performed using an optimal transmission and reception beampair determined through a beam scanning operation between a terminal anda base station.

Furthermore, in accordance with an embodiment of the present invention,the number of bits necessary for information forwarding can be minimizedbecause a base station transmits indication information for a beam stageby stage.

Furthermore, in accordance with an embodiment of the present invention,overhead for the downlink control channel reception of a terminal can bereduced because the terminal monitors only a specific region in order toreceive the downlink control channel.

Furthermore, in accordance with an embodiment of the present invention,a base station can transmit downlink control channels at the same timeusing one or more frequencies because a resource region for atransmission beam set is allocated according to a frequency divisionmultiplexing method.

Effects which may be obtained in the present invention are not limitedto the above-described effects, and other technical effects notdescribed above may be evidently understood by a person having ordinaryskill in the art to which the present invention pertains from thefollowing description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included herein as a part of adescription in order to help understanding of the present disclosure,provide embodiments of the present disclosure, and describe thetechnical features of the present disclosure with the description below.

FIG. 1 is a diagram showing an example of a general system structure ofNR to which a method proposed in this specification may be applied.

FIG. 2 shows an example of a block diagram of a transmitter configuredwith an analog beamformer and RF chains.

FIG. 3 shows an example of a block diagram of a transmitter configuredwith a digital beamformer and RF chains.

FIG. 4 shows an example of a transmitter structure of hybrid beamformingaccording to various embodiments of the present invention.

FIG. 5 shows an example of a hybrid beamformer configuration accordingto various embodiments of the present invention.

FIG. 6 shows a beam bound vector and a beam gain/steering vectoraccording to various embodiments of the present invention.

FIG. 7 shows an accumulated beam pattern to which analog beamforming anddigital beamforming is applied according to various embodiments of thepresent invention.

FIG. 8 shows examples of analog beam scanning methods according tovarious embodiments of the present invention.

FIG. 9 shows examples of transmission/reception beam scanning operationsaccording to various embodiments of the present invention.

FIG. 10 shows an example of a method of designating a beam scanningsubframe according to various embodiments of the present invention.

FIG. 11 shows an example of a frame structure including a preamble forproviding indication information for a transmission beam according to anembodiment of the present invention.

FIG. 12 shows an example of a Tx beam set-based resource region for adownlink control channel according to various embodiments of the presentinvention.

FIG. 13 shows an operation flowchart of a terminal that receives adownlink channel according to various embodiments of the presentinvention.

FIG. 14 illustrates a block diagram of a wireless communication deviceto which methods proposed in this specification may be applied.

MODE FOR INVENTION

Some embodiments of the present disclosure are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings is intended to describesome exemplary embodiments of the present disclosure and is not intendedto describe a sole embodiment of the present disclosure. The followingdetailed description includes more details in order to provide fullunderstanding of the present disclosure. However, those skilled in theart will understand that the present disclosure may be implementedwithout such more details.

In some cases, in order to avoid making the concept of the presentdisclosure vague, known structures and devices are omitted or may beshown in a block diagram form based on the core functions of eachstructure and device.

In the present disclosure, a base station has the meaning of a terminalnode of a network over which the base station directly communicates witha terminal. In this document, a specific operation that is described tobe performed by a base station may be performed by an upper node of thebase station according to circumstances. That is, it is evident that ina network including a plurality of network nodes including a basestation, various operations performed for communication with a terminalmay be performed by the base station or other network nodes other thanthe base station. The base station (BS) may be substituted with anotherterm, such as a fixed station, a Node B, an evolved-NodeB (eNB), a basetransceiver system (BTS), or an access point (AP). Furthermore, theterminal may be fixed or may have mobility and may be substituted withanother term, such as user equipment (UE), a mobile station (MS), a userterminal (UT), a mobile subscriber station (MSS), a subscriber station(SS), an advanced mobile station (AMS), a wireless terminal (WT), amachine-type communication (MTC) device, a machine-to-Machine (M2M)device, or a device-to-device (D2D) device.

Hereinafter, downlink (DL) means communication from a base station toUE, and uplink (UL) means communication from UE to a base station. InDL, a transmitter may be part of a base station, and a receiver may bepart of UE. In UL, a transmitter may be part of UE, and a receiver maybe part of a base station.

Specific terms used in the following description have been provided tohelp understanding of the present disclosure, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present disclosure.

The following technologies may be used in a variety of wirelesscommunication systems, such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and non-orthogonalmultiple access (NOMA). CDMA may be implemented using a radiotechnology, such as universal terrestrial radio access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asglobal system for mobile communications (GSM)/general packet radioservice (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of electricaland electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is part of a universalmobile telecommunications system (UMTS). 3rd generation partnershipproject (3GPP) Long term evolution (LTE) is part of an evolved UMTS(E-UMTS) using evolved UMTS terrestrial radio access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by standarddocuments disclosed in at least one of IEEE 802, 3GPP and 3G PP2, thatis, radio access systems. That is, steps or parts not described in orderto clearly explain the technical spirit of the present invention in theembodiments of the present invention may be supported by the documents.Furthermore, all terms disclosed in this document may be described bythe standard documents.

In order to clarity the description, a 3GPP LTE/LTE-A/new RAT (NR)system is basically described, but the technical characteristics of thepresent invention are not limited thereto.

Definition of Terms

eLTE eNB: An eLTE eNB is an evolution of an eNB that supports aconnection for an EPC and an NGC.

gNB: A node for supporting NR in addition to a connection with an NGC

New RAN: A radio access network that supports NR or E-UTRA or interactswith an NGC

Network slice: A network slice is a network defined by an operator so asto provide a solution optimized for a specific market scenario thatrequires a specific requirement together with an inter-terminal range.

Network function: A network function is a logical node in a networkinfra that has a well-defined external interface and a well-definedfunctional operation.

NG-C: A control plane interface used for NG2 reference point between newRAN and an NGC

NG-U: A user plane interface used for NG3 reference point between newRAN and an NGC

Non-standalone NR: A deployment configuration in which a gNB requires anLTE eNB as an anchor for a control plane connection to an EPC orrequires an eLTE eNB as an anchor for a control plane connection to anNGC

Non-standalone E-UTRA: A deployment configuration an eLTE eNB requires agNB as an anchor for a control plane connection to an NGC.

User plane gateway: A terminal point of NG-U interface

General System

FIG. 1 is a diagram illustrating an example of an overall structure of anew radio (NR) system to which a method proposed by the presentdisclosure may be implemented.

Referring to FIG. 1, an NG-RAN is composed of gNBs that provide an NG-RAuser plane (new AS sublayer/PDCP/RLC/MAC/PHY) and a control plane (RRC)protocol terminal for a UE (User Equipment).

The gNBs are connected to each other via an Xn interface.

The gNBs are also connected to an NGC via an NG interface.

More specifically, the gNBs are connected to a Access and MobilityManagement Function (AMF) via an N2 interface and a User Plane Function(UPF) via an N3 interface.

New RAT (NR) numerologies and frame structure

In the NR, a plurality of numerologies is supported.

The numerology is defined by a subcarrier spacing and CP overhead. Aplurality of subcarrier spacings may be derived by scaling a basicsubcarrier spacing with an integer N.

Although a used numerology is assumed to not use a very low subcarrierspacing in a very high carrier frequency, it may be selectedindependently of a frequency band.

A flexible network and UE channel bandwidth are supported.

In the RAN1 spec. viewpoint, a maximum channel bandwidth per NR carrieris 400 MHz.

In the case of at least one numerology, candidates corresponding to amaximum number of subcarriers per NR carrier are 3300 or 6600 in theRAN1 spec. viewpoint.

Subframe duration is fixed to 1 ms, and a frame length is 10 ms.

A scalable numerology needs to permit a subcarrier spacing of at least15 kHz-480 kHz.

All numerologies having a large subcarrier spacing of 15 kHz or moreregardless of CP overhead are arranged in a symbol bound every 1 ms ofan NR carrier.

More specifically, normal CP series are selected as follows.

-   -   If a subcarrier spacing is 15 kHz*2^(n) (n is an integer not a        negative number),    -   Each symbol length (including a CP) of a 15 kHz subcarrier        spacing is the same as the sum of 2^(n) symbols corresponding to        a scaled subcarrier spacing.    -   All OFDM symbols within 0.5 ms other than the first OFDM symbol        has the same size every 0.5 ms.    -   The first OFDM symbol within 0.5 ms is 16 Ts (15 kHz and an FFT        size of 2048 are assumed) longer than other OFDM symbols.    -   16 Ts are used in a CP for the first symbol.    -   If a subcarrier spacing is 15 kHz*2^(n) (n is a negative        integer)    -   Each symbol length (including a CP) of a subcarrier spacing is        the same as the sum of corresponding 2^(n) symbols of 15 kHz.

A resource defined by one subcarrier and one symbol is called a resourceelement (RE).

A physical layer design supports an extended CP.

An extended CP is only one in a given subcarrier spacing. An LTE-scaledextended CP is supported in at least 60 kHz subcarrier spacing. A CPtype may be semi-statically configured using UE-specific signaling.

A UE supporting an extended CP may depend on a UE type/capability.

The number of subcarriers per PRB is 12.

An explicit DC subcarrier has not been reserved with respect to both thedownlink and uplink.

The DC processing of a DC subcarrier on the transmitter side isregulated as follows with respect to DC present within a transmitter:

-   -   A receiver needs to be aware of where a DC subcarrier is located        or it is known where a DC subcarrier is located (by spec. or        signaling) or whether a DC subcarrier is not present within a        receiver bandwidth.    -   With respect to the downlink, a UE may assume that a DC        subcarrier transmitted by the transmitter (gNB) side has been        modulated. That is, data is not rate-matched or not punctured.    -   In the case of the uplink, a DC subcarrier transmitted by the        transmitter (UE) side is modulated. That is, data is not        rate-matched or not punctured.    -   In the case of the uplink, if a transmitter DC subcarrier on the        transmitter (UE) side is possible, a collision with at least        DMRS needs to be avoided.    -   With respect to the uplink, at least one specific subcarrier        needs to be defined as the candidate location of a DC        subcarrier. For example, the DC subcarrier is located at the        bound of a PRB.    -   In the case of the uplink, means by which a receiver determines        a DC subcarrier location needs to be designated.    -   This is associated with a DC subcarrier location written in        semi-static signaling from a UE and the standard.    -   If a DC subcarrier is not present, all subcarriers within a        receiver bandwidth are transmitted.

In contrast, special handling of a DC subcarrier in the RAN1 has notbeen regulated on the receiver side, and an operation thereof remains asan implementation. That is, the receiver may puncture data received inthe DC subcarrier, for example.

A slot is defined as 7 or 14 OFDM symbols with respect to the samesubcarrier spacing up to 60 kHz having a normal CP and as 14 OFDMsymbols at the same subcarrier spacing higher than 60 kHz having anormal CP.

A slot may include all downlinks, all uplinks or {at least one downlinkpart and at least one uplink part}.

A slot set is supported. That is, data transmission may be scaled as oneor a plurality of slot intervals.

A mini-slot having the following length is defined.

-   -   a mini-slot having at least 6 GHz or more, length 1 symbol is        supported.    -   Lengths from a length 2 to a slot length−1    -   In the case of URLLC, minimum two are supported.

Upon designing the slot level channel/signal/procedure, the followingcontents need to be taken into consideration.

-   -   A possible occurrence of a mini-slot/slot transmission(s)        occupying resources scheduled for an ongoing slot        transmission(s) of a given carrier with respect to the        same/different UEs    -   At least one of a DMRS format/structure/configuration for a slot        level data channel is reused for a mini-slot level data channel.    -   At least one of a DL control channel        format/structure/configuration for slot level data scheduling is        designed to be applicable to mini-slot level data scheduling.    -   At least one of an UL control channel        format/structure/configuration for slot level UCI feedback is        designed to be applicable to mini-slot level UCI feedback.

The following use cases for designing a mini-slot need to be taken intoconsideration.

-   -   Support of a very low latency time including URLLC for a        specific slot length    -   A target slot length is a minimum of 1 ms, 0.5 ms.    -   In particular, if a Transmission/Reception Point (TRP) uses        beam-sweeping (e.g., 6 GHz or more), a finer TDM unit        (granularity) for the same or different UEs within a slot is        supported.    -   NR-LTE co-existence    -   Forward compatibility for a non-licensed spectrum operation

Beam Management

In the NR, beam management is defined as follows.

Beam management: a set of L1/L2 procedures for acquiring and maintaininga set of TRP(s) that may be used for DL and UL transmission andreception and/or UE beams, and includes at least the following contents:

-   -   Beam determination: an operation of selecting its own        transmission/reception beam by a TRP(s) or a UE.    -   Beam measurement: an operation of measuring the characteristics        of a received beamforming signal by a TRP(s) or a UE.    -   Beam reporting: an operation of reporting information of a        beamformed signal by a UE based on beam measurement.    -   Beam sweeping: an operation of covering a space region using a        beam transmitted and/or received during a time interval        according to a predetermined method.

Furthermore, a Tx/Rx beam correspondence in a TRP and a UE is defined asfollows.

-   -   A Tx/Rx beam correspondence in a TRP is maintained when at least        one of the followings is satisfied.    -   A TRP may determine a TRP reception beam for an uplink reception        based on the downlink measurement of a UE for one or more        transmission beams of the TRP.    -   A TRP may determine a TRP Tx beam for downlink transmission        based on the uplink measurement of the TRP for one or more Rx        beams of the TRP.    -   A Tx/Rx beam correspondence in a UE is maintained when at least        one of the followings is satisfied.    -   A UE may determine a UE Tx beam for uplink transmission based on        the downlink measurement of the UE for the one or more Rx beams        of the UE.    -   A UE may determine a UE reception beam for downlink reception on        the basis of the indication of a TRP based on uplink measurement        for one or more Tx beams.    -   The capability indication of UE beam correspondence-related        information is supported for a TRP.

The following DL L1/L2 beam management procedure is supported within oneor a plurality of TRPs.

P-1: this is used to make possible UE measurement for different TRP Txbeams in order to support the selection of a TRP Tx beam/UE Rx beam(s).

-   -   In general, beamforming in a TRP includes intra/inter-TRP Tx        beam sweep in different beam sets. For beamforming in a UE, in        general, this includes UE Rx beam sweep from different sets of        beams.

P-2: this is used so that UE measurement for different TRP Tx beamschanges an inter/intra-TRP Tx beam(s).

P-3: UE measurement for the same TRP Tx beam is used to change a UE Rxbeam if a UE uses beamforming.

Aperiodic reporting triggered by at least network is supported in theP-1, P-2 and P-3-related operation.

UE measurement based on an RS for beam management (at least CSI-RS) isconfigured with K (total number of beams) beam. A UE reports themeasured results of selected N Tx beams. In this case, N is essentiallynot a fixed number. A procedure based on an RS for a mobility object isnot excluded. Report information includes information indicatingmeasurement quantity for an N beam(s) and N DL transmission beam if atleast N<K. In particular, a UE may report a CSI-RS resource indicator(CRI) of N′ with respect to K′>1 non-zero-power (NZP) CSI-RS resources.

A UE may be configured as the following higher layer parameters for beammanagement.

-   -   N≥1 reporting setting, M≥1 resource configuration    -   Links between reporting setting and resource configurations are        established in an agreed CSI measurement configuration.    -   CSI-RS-based P-1 and P-2 are supported as resource and reporting        setting.    -   P-3 may be supported regardless of whether reporting setting is        present.    -   Reporting setting including at least the following contents    -   Information indicating a selected beam    -   L1 measurement reporting    -   A time domain operation (e.g., aperiodic operation, periodic        operation, semi-persistent operation)    -   Frequency granularity when several frequency granularities are        supported    -   Resource setting including at least the following contents    -   Time domain operation (e.g., aperiodic operation, periodic        operation, semi-persistent operation)    -   RS type: at least NZP CSI-RS    -   At least one CSI-RS resource set. Each CSI-RS resource set        includes K≥1 CSI-RS resources (some parameters of K CSI-RS        resources may be the same. For example, a port number, a time        domain operation, density and a period)

Furthermore, NR supports the following beam reporting by taking intoconsideration L groups, that is, L>1.

-   -   Information indicating a minimum group    -   Measurement quantity for an N1 beam (L1 RSRP and CSI reporting        support (if a CSI-RS is for CSI acquisition))    -   If applicable, information indicating N_(I) DL transmission        beams

Group-based beam reporting, such as that described above, may beconfigured in a UE unit. Furthermore, the group-based beam reporting maybe turned off in a UE unit (e.g., when L=1 or N₁=1).

The NR supports that a UE can trigger a mechanism recovering from a beamfailure.

A beam failure event occurs when quality of a beam pair link ofassociated control channels is sufficiently low (e.g., a comparison witha threshold, the timeout of an associated timer). The mechanismrecovering from a beam failure (or blockage) is triggered when beamblockage occurs.

A network explicitly configures a UE having a resource for transmittingan UL signal for the purpose of recovery. The configuration of theresources is supported in the place where a base station listens in allor some directions (e.g., random access region).

An UL transmission/resource reporting beam blockage may be located in aPRACH (resource orthogonal to a PRACH resource) and at the same timeinstance or a time instance (may be configured for a UE) different fromthat of a PRACH. The transmission of a DL signal is supported so that aUE can monitor a beam in order to identify new potential beams.

The NR supports beam management regardless of beam-related indication.If the beam-related indication is provided, information regarding aUE-side beamforming/reception procedure used for CSI-RS-basedmeasurement may be indicated through QCL with respect to the UE.

Parameters for delay, Doppler, and an average gain used in the LTEsystem and a space parameter for beamforming in a receiver are expectedto be added as QCL parameters to be supported in the NR. An angle ofarrival-related parameter in a terminal reception beamforming viewpointand/or angle of departure-related parameters in a base station receptionbeamforming viewpoint may be included.

The NR supports to use the same or different beams in a control channeland corresponding data channel transmission.

For NR-PDCCH transmission supporting robustness for beam pair linkblocking, a UE may be configured to monitor an NR-PDCCH on M beam pairlinks at the same time. In this case, M≥1 and a maximum value of M maydepend on at least a UE capability.

A UE may be configured to monitor an NR-PDCCH on a different beam pairlink(s) in different NR-PDCCH OFDM symbols. A parameter related to a UERx beam configuration for monitoring an NR-PDCCH on a plurality of beampair links may be configured by higher layer signaling or a MAC CEand/or is taken into consideration in the discovery space design.

At least the NR supports the indication of space QCL assumption betweena DL RS antenna port(s) and a DL RS antenna port(s) for the demodulationof a DL control channel. A candidate signaling method for beamindication for an NR-PDCCH (i.e., configuration method of monitoring anNR-PDCCH) is MAC CE signaling, RRC signaling, DCI signaling, a spec.transparent and/or implicit method, and a combination of these signalingmethods.

For the reception of a unicast DL data channel, the NR supports theindication of space QCL assumption between a DL RS antenna port and theDMRS antenna port of a DL data channel.

Information indicating an RS antenna port is indicated through DCI(downlink permission). Furthermore, the information indicates an RSantenna port QCLed with a DMRS antenna port. A different set of DMRSantenna ports for a DL data channel may be indicated as QCL with respectto a different set of RS antenna ports.

Hybrid Beamforming

The existing beamforming technology using multiple antennas may bedivided into an analog beamforming scheme and a digital beamformingscheme depending on the location where a beamforming weightvector/precoding vector is applied.

The analog beamforming scheme is a beamforming scheme applied to aninitial multiple antenna structure. This may mean a scheme for branchingan analog signal on which digital signal processing has been completedinto a plurality of paths and forming a beam by applying a phase shift(PS) and power amplifier (PA) configuration to each path.

For analog beamforming, there is a need for a structure in which the PAand PS connected to each antenna process an analog signal derived fromone digital signal. In other words, the PA and PS of an analog stageprocess a complex weight.

FIG. 2 shows an example of a block diagram of a transmitter configuredwith an analog beamformer and RF chains. FIG. 2 is merely forconvenience of description and does not limit the range of the presentinvention.

In FIG. 2, the RF chain means a processing block in which a baseband(BB) signal is converted into an analog signal. In the analogbeamforming scheme, the accuracy of a beam is determined depending onthe characteristics of a PA and PS. The analog beamforming scheme may beadvantageous in narrowband transmission in terms of control of thedevices.

Furthermore, the analog beamforming scheme has a relatively smallmultiplexing gain for a transfer rate increase because it is configuredwith a hardware structure that is difficult to implement multiple streamtransmission. Furthermore, in this case, beamforming for each orthogonalresource allocation-based terminal may not be easy.

In contrast, in the digital beamforming scheme, in order to maximizediversity and a multiplexing gain in a MIMO environment, beamforming isperformed in a digital stage using a baseband (BB) process.

FIG. 3 shows an example of a block diagram of a transmitter configuredwith a digital beamformer and RF chains. FIG. 3 is merely forconvenience of description and does not limit the range of the presentinvention.

In the case of FIG. 3, beamforming may be performed as precoding isperformed in a BB process. In this case, an RF chain includes a PA. Thereason for this is that in the digital beamforming scheme, a complexweight derived for beamforming is directly applied to transmission data.

Furthermore, multiple user beamforming may be supported at the same timebecause different beamforming may be performed for each terminal.Furthermore, the flexibility of scheduling is improved becauseindependent beamforming is possible for each terminal to which anorthogonal resource has been allocated. Accordingly, an operation of atransmitter complying with a system object is possible. Furthermore, inthe environment in which wideband transmission is supported, if atechnology, such as MIMO-OFDM, is applied, an independent beam may beformed for each subcarrier.

Accordingly, the digital beamforming scheme can maximize a maximumtransfer rate of one terminal (or user) based on a capacity increase ofa system and an enhanced beam gain. In the existing 3G/4G (e.g.,LTE(-A)) system, the digital beamforming-based MIMO scheme has beenintroduced based on characteristics, such as those described above.

In an NR system, a massive MIMO environment in which transmission andreception antenna greatly increases may be taken into consideration. Ingeneral, in cellular communication, a maximum of transmission andreception antennas applied to the MIMO environment is assumed to be 8.However, as a massive MIMO environment is taken into consideration, thenumber of transmission and reception antennas may be increased to tensof or hundreds of transmission and reception antennas.

In this case, in the massive MIMO environment, if the above-describeddigital beamforming technology is applied, a transmitter needs toperform signal processing on hundreds of antennas through a BB processfor digital signal processing. Accordingly, the complexity of the signalprocessing may be greatly increased, and the complexity of a hardwareimplementation may be greatly increased because RF chains correspondingto the number of antennas are necessary.

Furthermore, the transmitter requires independent channel estimation forall the antennas. Furthermore, in the case of the FDD system, pilotand/or feedback overhead may excessively increase because thetransmitter requires feedback information for massive MIMO channelsconfigured with all the antennas.

In contrast, in the massive MIMO environment, if the above-describedanalog beamforming technology is applied, the hardware complexity of thetransmitter is relatively low.

In contrast, an increment of performance using multiple antennas is verysmall, and the flexibility of resource allocation may be reduced. Inparticular, upon wideband transmission, to control a beam for eachfrequency is not easy.

Accordingly, in the massive MIMO environment, only one of the analogbeamforming and digital beamforming schemes is not exclusively selected,but a hybrid type transmitter configuration method in which analogbeamforming and digital beamforming structures have been combined isnecessary.

In this case, a hybrid type transmitter may be configured using therelation between a performance gain and complexity of the analogbeamforming scheme and the digital beamforming scheme, such as thatshown in Table 1.

TABLE 1 beamforming accuracy Multiple Multiple Hardware Pilot andcontrol carrier beam stream complexity feedback easiness controltransmission (BB process) overhead Analog Low (PA/PS ImpossibleImpossible Low Low beamforming device or difficult or difficult schemecharacteristics and relation) Digital High Possible Possible High Highbeamforming scheme

That is, a hybrid type transmitter structure capable of reducing thehardware implementation complexity of a transmitter and obtaining amaximum beamforming gain using massive antennas based on the performancegain and complexity relation shown in Table 1 may be taken intoconsideration (or designed).

Hereinafter, a scheme in which a hybrid type transmitter forms a beammay be called a hybrid beamforming (scheme).

Hybrid Beamforming System Model

A basic hybrid beamformer (transmitter) may be configured as atransmitter structure having N_(t) ^(RF) independent antennas for eachRF chain as in FIG. 4.

FIG. 4 shows an example of a transmitter structure of hybrid beamformingaccording to various embodiments of the present invention. FIG. 4 ismerely for convenience of description and does not limit the range ofthe present invention.

Referring to FIG. 4, N_(s) is the number of transmission data streams,N_(RF) is a total number of RF chains, N_(t) ^(RF) is the number oftransmission antennas for each RF chain, N_(t) is a total number ofantennas of a transmitter, and N_(r) is a total number of antennas of areceiver.

In this case, a relation, such as Equation 1, may be established betweenthe total number of antennas N_(t) and the number of antennas for eachRF chain N_(t) ^(RF).

N _(t) =N _(t) ^(RF) ×N _(RF)  [Equation 1]

In this case, a system model of a matrix type, such as Equation 2, maybe taken into consideration because signals passing through a phaseshifter (PS) and a power amplifier (PA) for each RF chain areindependently transmitted through transmission antennas.

y _(k) =H _(k) F ^(RF) F _(k) ^(BB) s _(k) +z _(k)  [Equation 2]

In Equation 2, y_(k) means a received signal vector (N_(r)×1) in a k-thsubcarrier. H_(k) means N_(r)×N_(t) channels in the k-th subcarrier. F′means N_(t)×N_(t) RF precoders in all subcarriers. F_(k) ^(BB) meansN_(RF)×N_(s) baseband precoders in the k-th subcarrier. Furthermore,s_(k) means a transmission signal vector (N_(s)×1) in the k-thsubcarrier, and z_(k) means a noise signal vector (N_(r)×1) in the k-thsubcarrier.

In this case, the RF precoder is the same with respect to all thesubcarriers, and the baseband precoder may be changed for eachsubcarrier.

In this case, if Equation 2 is expanded with respect to a subcarrier k,Equation 3 may be derived.

$\mspace{635mu} {{\left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack \begin{bmatrix}y^{(1)} \\\vdots \\y^{(Nr)}\end{bmatrix}} = {{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1Nt} \\h_{21} & h_{22} & \ldots & h_{2Nt} \\\vdots & \vdots & \ddots & \vdots \\h_{Nr1} & h_{Nr2} & \ldots & h_{NrNt}\end{bmatrix}{F^{RF}\left( {\begin{bmatrix}v_{1,1} & v_{1,2} & \ldots & v_{N^{RF},N_{S}} \\v_{2,1} & v_{2,2} & \ldots & v_{N^{RF},N_{S}} \\\vdots & \vdots & \ddots & \vdots \\v_{N^{RF},1} & v_{N^{RF},2} & \ldots & v_{N^{RF},N_{s}}\end{bmatrix}\ \begin{bmatrix}x^{(1)} \\\vdots \\x^{({N_{S} - 1})}\end{bmatrix}} \right)}}\  + \begin{bmatrix}z^{(1)} \\\vdots \\z^{(Nr)}\end{bmatrix}}}$

In this case, an equivalent precoding matrix F^(RF) (N_(t)×N_(RF)matrix) of analog beamforming generated by a PS and PA after an RF chainmay be represented like Equation 4.

$\begin{matrix}{F^{RF} = \begin{bmatrix}w_{N_{t}^{RF}}^{1} & 0 & 0 & \ldots & 0 \\0 & w_{N_{t}^{RF}}^{2} & 0 & \ldots & 0 \\0 & 0 & w_{N_{t}^{RF}}^{3} & \ldots & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots \\0 & 0 & 0 & \ldots & w_{N_{t}^{RF}}^{N_{RF}}\end{bmatrix}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Through Equation 4, a precoding weight for each RF chain of the RFprecoding matrix F^(RF), such as Equation 5, may be calculated.

$\begin{matrix}{W_{N_{t}^{RF}}^{i} = \begin{bmatrix}w_{1}^{i} \\w_{2}^{i} \\\vdots \\w_{N_{t}^{RF}}^{i}\end{bmatrix}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Beam Radiation Pattern of Hybrid Beamforming

For hybrid beamforming, a uniform linear array (ULA) antenna may beused. In this case, the array response vector of the ULA antenna is thesame as Equation 6.

                                     [Equation  6]${a(\theta)} = \begin{bmatrix}1 & {\exp \left( {j\; 2\pi \times 1 \times \frac{d}{\lambda}{\sin (\theta)}} \right)} & {\exp \left( {j\; 2\; \pi \times 2 \times \frac{d}{\lambda}{\sin (\theta)}} \right)} & \ldots \\\; & {\exp \left( {j\; 2\; \pi \times \left( {N_{t} - 1} \right) \times \frac{d}{\lambda}{\sin (\theta)}} \right)} & \; & \;\end{bmatrix}^{T}$

In Equation 6, λ means a wave-length, and d means the distance betweenantennas. Hereinafter, for convenience of description, a case where thenumber of RF chains configuring a hybrid beamformer is 4 and the numberof analog antennas for each RF chain is 4 is assumed. In this case, thehybrid beamformer may be configured like FIG. 5.

FIG. 5 shows an example of a hybrid beamformer configuration accordingto various embodiments of the present invention. FIG. 5 is merely forconvenience of description and does not limit the range of the presentinvention.

Referring to FIG. 5, it is assumed that the hybrid beamformer has a16-ULA antenna structure configured with 4 RF chains. In this case, atotal number of transmission antennas is 16, and λ/2 is established. Inthis case, the phase shifter (PS) and power amplifier (PA) of an analogterminal may be represented as an equivalent beamforming weight, andthis is the same as Equation 7.

$\begin{matrix}{{F^{RF} = \begin{bmatrix}w_{N_{t}^{RF}}^{1} & 0 & 0 & 0 \\0 & w_{N_{t}^{RF}}^{2} & 0 & 0 \\0 & 0 & w_{N_{t}^{RF}}^{3} & 0 \\0 & 0 & 0 & w_{N_{t}^{RF}}^{4}\end{bmatrix}},{w_{N_{t}^{RF}}^{i} = \begin{bmatrix}w_{1}^{i} \\w_{2}^{i} \\w_{3}^{i} \\w_{4}^{i}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

In Equation 7, F^(RF) means an RF precoder.

In order to derive a beam pattern in a reference direction (boresight),the shift angle of a beam may be set to 0°. Accordingly, the elements ofall weight vectors of an analog precoding matrix become 1. In this case,a given rank-1 weight vector to be applied in a digital beamformingstage may be defined like Equation 8.

F ^(BB) =v ₁=[v ₁ v ₂ v ₃ v ₄]^(T)  [Equation 8]

In the reference direction (i.e., θ=0°), all antenna array responsevectors to which the beamforming of Equation 7 has been applied may berepresented like Equation 9. In this case, the distance d between theantennas is assumed to be λ/2. A response to each antenna array responsemay be represented as the sum of all vector elements.

                                     [Equation  9]${\sum{a(\theta)}} = {{\sum\limits_{i = 0}^{15}{a_{i}(\theta)}} = {{\left( {1 + {\exp \left( {j\; \pi \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 2 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 3 \times {\sin (\theta)}} \right)}} \right) \times v_{1}} + {\left( {{\exp \left( {j\; \pi \; 4 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 5 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 6 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 7 \times {\sin (\theta)}} \right)}} \right) \times v_{2}} + {\left( {{\exp \left( {j\; \pi \; 8 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 9 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 10 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 11 \times {\sin (\theta)}} \right)}} \right) \times v_{3}} + {\left( {{\exp \left( {j\; \pi \; 12 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 13 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 14 \times {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 15 \times {\sin (\theta)}} \right)}} \right) \times v_{4}}}}$

If Equation 9 is arranged, the results of Equation 10 may be obtained.

                                    [Equation  10] $\begin{matrix}{{\sum{a(\theta)}} = {\left( {1 + {\exp \left( {j\; \pi \; {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 2\; {\sin (\theta)}} \right)} + {\exp \left( {j\; \pi \; 3\; {\sin (\theta)}} \right)}} \right) \times}} \\{\left( {v_{1} + {{\exp \left( {j\; \pi \; 4\; {\sin (\theta)}} \right)} \cdot v_{2}} + {{\exp \left( {j\; \pi \; 8\; {\sin (\theta)}} \right)} \cdot v_{3}} +} \right.} \\\left. {\exp {\left( {j\; \pi \; 12\; {\sin (\theta)}} \right) \cdot v_{4}}} \right) \\{= {{\left( {\sum\limits_{i = 1}^{4}s_{i}} \right) \times \left( {\sum\limits_{i = 1}^{4}t_{i}} \right)} = {\sum{s \times {\sum t}}}}}\end{matrix}$

In Equation 10, s means a beam bound vector, and t means a beam gain anda steering vector. In this case, the s and the t may be represented likeEquation 11 and Equation 12, respectively.

$\begin{matrix}{s = \begin{bmatrix}1 \\e^{j\; \pi \; \sin \; {(\theta)}} \\e^{j\pi 2\sin \; {(\theta)}} \\e^{j\pi 3\sin \; {(\theta)}}\end{bmatrix}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack \\{t = {\begin{bmatrix}1 & 0 & 0 & 0 \\0 & e^{J^{\pi 4\sin \; {(\theta)}}} & 0 & 0 \\0 & 0 & e^{J^{\pi 8\sin \; {(\theta)}}} & 0 \\0 & 0 & 0 & e^{J^{\pi \; 12{\sin {(\theta)}}}}\end{bmatrix}\begin{bmatrix}v_{1} \\v_{2} \\v_{3} \\v_{4}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

In this case, the beam bound vector s may determine a total valid rangeof a beam. Furthermore, the range of digital beamforming may be limitedwithin a corresponding region. The vector s and the vector t may berepresented like FIG. 6.

FIG. 6 shows a beam bound vector and a beam gain/steering vectoraccording to various embodiments of the present invention. FIG. 6 ismerely for convenience of description and does not limit the range ofthe present invention.

Furthermore, finally, an accumulated beam pattern result to which thevector of Equation 8 for determining digital beamforming has beenapplied may be represented like FIG. 7.

FIG. 7 shows an accumulated beam pattern to which analog beamforming anddigital beamforming is applied according to various embodiments of thepresent invention. FIG. 7 is merely for convenience of description anddoes not limit the range of the present invention.

From FIG. 7, it may be seen that the valid range of a beam is determinedbased on the beam bound vector s shown in FIG. 6.

In the above-described part, a system model and radiation pattern inwhich one RF chain is mapped to some sub-arrays and analog beamcoefficients applied to a corresponding sub-array are the same have beendescribed. However, in the hybrid beamforming structure, mapping betweenvarious types of RF chains and antenna arrays in addition to the examplemay be taken into consideration. A method of configuring an analog beamcoefficient may be taken into consideration in various ways.

Analog Beam Scanning

In general, analog beamforming may be used in a pure analog beamformingtransmitter and receiver and a hybrid beamforming transmitter andreceiver. In this case, analog beam scanning may perform estimation onone beam at the same time. Accordingly, a beam training time necessaryfor beam scanning is proportional to a total number of candidate beams.

As described above, in the case of analog beamforming, a beam scanningprocess in the time domain is essentially necessary for transmitter andreceiver beam estimation. In this case, an estimation time T_(s) for alltransmission and reception beams may be represented like Equation 1.

T _(s) =t _(s)×(K _(T) ×K _(R))  [Equation 13]

In Equation 13, t_(s) means a time necessary for one beam scanning,K_(T) means the number of transmission beams, and K_(R) means the numberof reception beams.

FIG. 8 shows examples of analog beam scanning methods according tovarious embodiments of the present invention. FIG. 8 is merely forconvenience of description and does not limit the range of the presentinvention.

In the case of FIG. 8, it is assumed that a total number of transmissionbeams K_(T) is L and a total number of reception beams K_(R) is 1. Inthis case, a total number of candidate beams is L, and thus an L timeinterval is necessary in the time domain.

In other words, for analog beam estimation, only one beam estimation maybe performed in one time interval. As shown in FIG. 8, an L timeinterval is necessary to perform all L beams (P₁ to P_(L)) estimation.After an analog beam estimation procedure is terminated, a terminalfeeds the identification (e.g., ID) of a beam having the highest signalintensity back to a base station. That is, a longer training time may benecessary as the number of beams increases according to an increase inthe number of transmission and reception antennas.

In analog beamforming, a training interval for an individual beam needsto be guaranteed unlike in digital beamforming because the size of acontinuous waveform in a time domain and a phase angle are changed aftera digital-to-analog converter (DAC). Accordingly, as the length of thetraining interval increases, efficiency of a system may be reduced(i.e., a loss of a system may be increased).

As described above, if both a base station and a terminal perform analogbeamforming, for downlink transmission, the base station needs toperform an analog beam scanning operation for a transmission beamconfiguration, and the terminal needs to perform an analog beam scanningoperation for a reception beam configuration.

FIG. 9 shows examples of transmission/reception beam scanning operationsaccording to various embodiments of the present invention. FIG. 9 ismerely for convenience of description and does not limit the range ofthe present invention.

Referring to FIG. 9, it is assumed that a base station and a terminalperform a beam scanning operation in order to determine an optimal pairof a transmission beam and a reception beam.

Specifically, the base station transmits a preamble (e.g., referencesignal, pilot signal) for a plurality of transmission (Tx) candidatebeams (or candidate transmission (Tx) beam(s)). Accordingly, theterminal may identify an optimal pair of a transmission beam and areception beam by applying a reception (Rx) candidate beam (or candidatereception (Rx) beam(s)). In this case, the terminal needs to notify thebase station of information for a transmission beam to be applied by thebase station among information for identified transmission/receptionbeams.

However, a transmission/reception beam pair (Tx/Rx beam pair) betweenthe base station and the terminal identified according to theabove-described procedure may be different depending on a movement ofthe terminal. A change in an optimal transmission beam may occurdepending on a movement in the location of the terminal or a change inthe blockage environment around the terminal. A change in an optimalreception beam may occur due to a short-term change, such as therotation of a terminal, in addition to a long-term change. For example,in the case of a handset/handheld terminal, such as a smartphone, if auser moves his or her hand slightly while carrying the terminal, anoptimal reception beam needs to be changed because the reference axis ofthe terminal is changed.

Accordingly, the scanning/tracking operation of a reception beam needsto be frequently performed compared to the scanning/tracking operationof a transmission beam. In other words, if a time limit in whichtransmission beam scanning/tracking must occur (i.e., is required) isrepresented as N and a time limit in which reception beamscanning/tracking must occur is represented as M, the relation of M<Nmay be established.

In this case, in order to satisfy the relation of M<N, a method oftransmitting all preamble sets every M, that is, a smaller time of the Mand N, may be taken into consideration.

FIG. 10 shows an example of a method of designating a beam scanningsubframe according to various embodiments of the present invention. FIG.10 is merely for convenience of description and does not limit the rangeof the present invention.

Referring to FIG. 10, a case where a terminal performs only beamscanning on a preferred transmission beam in a No. 3 subframe 1002and/or a No. 6 subframe 1004 is assumed. The preferred transmission beamis selected every 9 subframes.

In this case, a base station needs to transmit a plurality of preamblesin the No. 3 subframe 1002 and/or the No. 6 subframe 1004 because aplurality of terminals may prefer different transmission beams.Accordingly, in the method, a resource in which data can be transmittedin a beam scanning subframe (i.e., Tx-Rx beam scanning subframe and/orRx beam scanning subframe) may be very limited. Accordingly, systemoverhead may increase.

Accordingly, in a beam scanning subframe in which a process of searchingfor (or identifying) an optimal Tx/Rx beam pair is performed, a methodconfigured based on transmission beam scanning/tracking duration N maybe taken into consideration.

In this case, as described above, the reception beam scanning/trackingoperation needs to be performed more frequently within the correspondingduration (i.e., transmission beam scanning/tracking duration).

For the reception beam scanning/tracking operation, the presentinvention proposes a method of transmitting, by a base station,information for a transmission beam indication to a terminal andobtaining, by the terminal, the information.

Specifically, the base station may use a transmission method of asignature (i.e., a preamble type) using a reference signal or atransmission method of a message type through a specific physicalchannel in order to transmit the information for the transmission beamindication.

First Embodiment

In an embodiment of the present invention, a base station may transmitone or a plurality of preambles (e.g., reference signal, pilot signal)to be used for at least one of the following two objects during aspecific time interval within a subframe.

-   -   the identification of a transmission beam (or an indicator for a        transmission beam) applied to a physical layer channel (e.g.,        PDSCH, PDCCH) transmitted in a corresponding subframe    -   Reception beam scanning/tracking for a terminal that requires        reception beam scanning/tracking within a shorter time compared        to transmission beam scanning/tracking

FIG. 11 shows an example of a frame structure including a preamble forproviding indication information for a transmission beam according to anembodiment of the present invention. FIG. 11 is merely for convenienceof description and does not limit the range of the present invention.

Referring to FIG. 11, a case where a base station performs atransmission beam scanning/tracking operation at 9 subframe intervals isassumed.

In this case, in a frame structure shown in FIG. 11, a beam scanningsubframe may be configured because a subframe is configured with only apreamble(s) used for the object of reception beam scanning and/ortransmission beam scanning.

Furthermore, a preamble may be used for various objects that may beperformed as the existing reference signal (RS) in addition to theabove-described two objects. For example, the preamble may be used forthe estimation of channel state information for the downlink, themeasurement of radio resource management (RRM), such as reference signalreceived power (RSRP)/reference signal received quality (RSRQ)/receivedsignal strength indicator (RSSI) and/or a channel estimation object forphysical channel demodulation transmitted in a corresponding subframe.

In this case, in order to improve efficiency of beamforming switching inthe RF stage with respect to the configuration of a subframe proposed inthe present invention, the preamble may be transmitted in initial Ktransmission symbols (i.e., symbols used for transmission) of thesubframe.

In this case, the K value may include 0. When the K value is set to 0, acorresponding subframe may mean a subframe to which specific beamformingis not applied. Alternatively, to set the K value to 0 may mean that thepreamble is not used for the object of the identification of atransmission beam applied to a physical layer channel transmitted in thecorresponding subframe.

The K value may be forwarded using one method of the following examples.

For example, according to a dynamic adaptation method, the K value maybe forwarded in a signature type through the sequence of a preamblefirst transmitted in a corresponding subframe.

For another example, according to the dynamic adaptation method, the Kvalue may be forwarded in a signature type through each preamblesequence. More specifically, the signature may have been related towhether a preamble transmitted in a next symbol is present.

For another example, according to the dynamic adaptation method, aseparate physical channel and/or signal used to notify the K value maybe defined. In this case, a base station may deliver the K value to aterminal through the defined physical channel and/or signal.

For another example, according to a semi-static adaptation method, the Kvalue may be forwarded through higher layer information. Morespecifically, a base station may transmit the K value to a terminalthrough higher layer signaling (e.g., radio resource control (RRC)signaling).

Furthermore, with respect to a preamble finally transmitted in acorresponding subframe among preambles proposed in the presentinvention, a method of applying the same transmission beam as atransmission beam to be applied to a physical channel (e.g., PDSCH,PDCCH) transmitted in the corresponding subframe may also be taken intoconsideration. However, in this case, it is a prerequisite that thepreamble is used for the object of the identification of a transmissionbeam applied to a physical layer channel transmitted in a correspondingsubframe.

In an embodiment of the present invention, if a proposed preamble signalis used for a reception beam scanning object (i.e., second object), thepreamble signal may be transmitted through a plurality of symbols. Forexample, in FIG. 9, if one symbol is configured (or constructed) for oneterminal reception beam, one preamble may be configured with a pluralityof sub-preambles, that is, a plurality of symbols. In this case, the Kvalue may mean the number of preambles or the number of sub-preambles.

In particular, as in a subframe example 2 shown in FIG. 11, a case wherethe preamble of a reception beam scanning object (i.e., an RS for a Txbeam #y shown in FIG. 11) and the preamble of a Tx beam identificationobject (i.e., an RS for a Tx beam #x shown in FIG. 11) are transmittedin the same subframe may be taken into consideration. In this case, thepreamble of the reception beam scanning object may be configured with Nsymbols in which the length of a symbol is y millisecond (msec), and thepreamble of the Tx beam identification object may be configured withsymbols in which the length of a symbol is z msec. In this case, the Nmeans the number of Rx candidate beams.

In this case, a method of designing the z as N×y (i.e., z=N×y) or amethod of designing the z as y (z=y) is possible. In the latter case,the preamble of the reception beam scanning object length may bedesigned to be N times longer than the preamble of the transmission beamidentification object.

A terminal may perform the following operation in accordance with theabove-described preamble transmission operation of a base station.

A terminal that requires reception beam scanning/tracking within a timefaster than that of transmission (Tx) beam scanning/tracking, amongterminals whose reporting and/or setting for a preferred transmissionbeam has been completed, may identify whether a preamble (e.g.,reference signal, pilot signal) corresponding to the preferredtransmission beam has been transmitted every subframe. If a preamblecorresponding to the preferred transmission beam is present through theidentification, the terminal may perform a scanning/tracking operationon a reception beam in a subframe in which the preamble has beendetected.

In this case, the preamble may have a structure in which a signalincluding beam identification (beam identifier, beam ID) information isearly transmitted. In applying the technology proposed in the presentinvention, the reception beam scanning/tracking time of a terminal canbe more secured as a beam identification is detected within a shortertime, thereby improving efficiency.

Accordingly, in the transmission of the preamble, after a signalcontaining beam identification information (e.g., a signal in which abeam identification is mapped to a sequence and configured in asignature type) is early transmitted, the preamble may be performedthrough a structure in which another signal to which the same Txbeamforming coefficient has been applied is transmitted.

Furthermore, a terminal having downlink data and/or control informationto be received, among terminals whose reporting and/or setting for apreferred transmission beam has been completed, may identify whether apreamble (e.g., reference signal, pilot signal) corresponding to thepreferred transmission beam has been transmitted every subframe. If apreamble corresponding to the preferred transmission beam is presentthrough the identification, the terminal may identify (acquire ordetect) downlink data and/or control information in a subframe in whichthe preamble has been detected. In this case, a terminal with which thepreamble for the transmission beam is matched (i.e., a terminal thatprefers the transmission beam) may additionally perform ascanning/tracking operation on a reception beam using the correspondingpreamble.

Second Embodiment

Furthermore, in another embodiment of the present invention, a preamble(i.e., a signature type using a reference signal), such as thatdescribed above, and a message type through a specific physical channelmay be used in order to transmit information for transmission beamindication. This may be similar to a case where in the legacy LTEsystem, control format indicator (CFI) information is transmittedthrough a physical control format indicator channel (PCFICH).

In this case, the specific physical channel proposed in the presentinvention is transmitted through a symbol more positioned on the frontside than a downlink control channel (physical control channel) (e.g.,PDCCH) as in the above-proposed preamble.

The method of transmitting information on transmission beam indication,which is proposed in the present invention, that is, a method ofindicating a transmission beam, may be used for the reception of acontrol channel and data channel by a terminal. However, if a beam usedfor the transmission of a data channel is different from a beam used forthe transmission of a control channel, the method proposed in thepresent invention may be used for only a downlink control channel.

Third Embodiment

Furthermore, in yet another embodiment of the present invention, if aterminal uses a preamble (e.g., a reference signal) for transmittingtransmission beam indication information or a plurality of beams inorder to receive a physical channel, the preamble or the physicalchannel may be repetitively transmitted in a plurality of timedomains/frequency domains. Accordingly, the terminal may be configuredto receive the preamble or physical channel by applying differentreception beams every plural time domains and/or frequency regions.

In this case, when the number of transmission candidate beams (i.e.,beam preferred by a terminal) is many, overhead of a preamble orphysical channel (i.e., channel resource) for the above-describeddynamic beam identification may occur.

When this point is taken into consideration, a method of restricting (orproposing) the size of a candidate beam set to be indicated in a timeunit (e.g., subframe of legacy LTE) in which downlink controlinformation (DCI) may be transmitted to N bits and dynamically providingnotification of a beam set to be used may be taken into consideration.In this case, some of beams included in the beam set may be included ina different beam set. For example, a beam #1, a beam #2, and a beam #3may be included in a beam set #1, and a beam #2, a beam #3, and a beam#4 may be included in a beam set #2.

In this case, which beam set can be used for which time/frequencyresource unit, by grouping all candidate beams into a plurality of beamsets may be previously designated according to a specific rule.Alternatively, a base station may transfer (or transmit) correspondinginformation to a terminal through signaling (e.g., signaling using anRRC message, signaling using a medium access control control element(MAC CE)).

Specifically, in order to configure a beam of a control channel, thatis, to transfer (or transmit) transmission beam information for acontrol channel to the terminal, the base station may use signalingmethods, such as the following examples.

For example, a base station may transfer (or transmit) transmission beaminformation for a control channel to a terminal through 1 levelsignaling. In this case, the configuration of a beam set needs to beconfigured by a predetermined rule. That is, a PDCCH Tx beam ID (e.g.,CSI-RS resource ID) needs to be previously determined based on a slotand/or a physical resource block (PRB) index. In this case, the basestation may notify the terminal of information for a transmission beamthrough dynamic beam indication based on downlink control information(DCI) and/or a downlink reference signal (DL RS). Alternatively, thebase station may notify the terminal of information for a transmissionbeam through dynamic beam indication based on a MAC CE.

For another example, a base station may transfer (or transmit)transmission beam information for a control channel to a terminalthrough 2 level signaling. Specifically, the base station may transfer(or transmit) information on beam set configuration to the terminalthrough RRC signaling, and may perform dynamic beam indication on theterminal using DCI and/or a DL RS. Alternatively, the base station maytransfer (or transmit) information on a beam set configuration to theterminal through RRC signaling, and may perform dynamic beam indicationon the terminal using a MAC CE. Alternatively, the base station maytransmit information on a beam set configuration to the terminal througha MAC CE, and may perform dynamic beam indication on the terminal usingDCI and/or a DL RS.

For another example, a base station may transfer (or transmit)transmission beam information for a control channel to a terminalthrough 3 level signaling. Specifically, the base station may transmithigher configuration information of a beam set (i.e., beam super setconfiguration) to the terminal through RRC signaling, may transmit lowerconfiguration information of a beam set (i.e., beam set configuration)within the super configuration information of the beam set to theterminal using a MAC CE, and may perform dynamic beam indication on theterminal using DCI and/or a DL RS. In other words, the base station mayuse RRC signaling for beam set configuration information of a wide rangeand use a MAC CE for beam set configuration information of a narrowrange included in the wide range in order to transmit information on theconfiguration of a beam set to the terminal.

FIG. 12 shows an example of a Tx beam set-based resource region for adownlink control channel according to various embodiments of the presentinvention. FIG. 12 is merely for convenience of description and does notlimit the range of the present invention.

Referring to FIG. 12, it is assumed that transmission beams of a basestation are grouped into 4 transmission beam sets (i.e., a Tx beam set#1, a Tx beam set #2, a Tx beam set #3, and a Tx beam set #4).Furthermore, a time/frequency scheduling resource unit in FIG. 12 may beconfigured as a resource block (RB) (e.g., RB of legacy LTE).

In this case, the base station may determine a plurality of resourceregions by splitting the resource region every 5 RBs in a frequency axisand every 2 subframes in a time axis, and may notify a terminal thatwhich transmission beam of the base station can be used in a specificresource region. For example, the base station may transmit a controlchannel in a region 1202, a region 1210 and/or a region 1216 using atransmission beam set #1, may transmit a control channel in a region1206, a region 1212 and/or the region 1220 using a transmission beam set#2, may transmit a control channel in a region 1204 and/or a region 1218using a transmission beam set #3, and may transmit a control channel ina region 1208 and/or a region 1214 using a transmission beam set #4.

Accordingly, the terminal may limit a region in which a control channelwill be monitored based on report information on a preferred beam of thebase station and/or information on a serving beam(s) designated in theterminal by the base station. In this case, as described above,information for a beam used for each scheduling resource (e.g., RB)within each resource region may be dynamically signaled through areference signal or a physical channel. In this case, the number of bitsnecessary for information forwarding can be minimized becauseinformation that requires signaling is limited to beams included in acorresponding beam set.

In the above-described method, a method of restricting the size of atransmission beam set of a base station to 1 (i.e., the number of beamsincluded in a transmission beam set is 1) may also be taken intoconsideration. In other words, if a transmission beam of a base stationto be used as a specific time/frequency resource unit is designated by adetermined rule or signaling (e.g., RRC message, signaling based on aMAC CE), a terminal may perform detection on a control channel only in acorresponding resource based on beam report information or beamindication information of the base station. In this case, the detectionmay mean blind detection for a control channel (e.g., PDCCH). In thiscase, a dynamic Tx beam indication method using a reference signal or aspecific physical channel, such as that described above, may not beapplied.

Alternatively, a method of not applying a dynamic transmission beamindication method although the size of a transmission beam set of a basestation is greater than 1 may also be taken into consideration. In thiscase, the base station may transmit a control channel using a pluralityof beams included in a corresponding resource region. For example, if acontrol channel is transmitted using 2 orthogonal frequency divisionmultiplexing (OFDM) symbols and the size of a transmission beam set is2, the base station may transmit the control channel through atransmission method of alternately using two beams. Furthermore, thebase station may transmit the control channel by applying differentbeams, included in a transmission beam set, to specific subcarrier setsin a frequency axis even within one symbol (i.e., OFDM symbol).

In the above-described method, if a terminal has a plurality of servingbeams (e.g., if a plurality of preferred beams is reported to the basestation or a plurality of beams is indicated by the base station), theterminal may perform blind detection in one or more PDCCH monitoringresource regions in which at least one beam of the plurality of servingbeams is included.

FIG. 13 shows an operation flowchart of a terminal that receives adownlink channel according to various embodiments of the presentinvention. FIG. 13 is merely for convenience of description and does notlimit the range of the present invention.

Referring to FIG. 13, it is assumed that a base station and a terminalperform a beam scanning operation in order to identify the best beampair. Furthermore, it is assumed that the base station and the terminalof FIG. 13 perform an operation according to the above-describedembodiments of the present invention (e.g., the contents related toFIGS. 10 to 12).

At step S1305, the terminal receives, from the base station, beamconfiguration information for a plurality of transmission beams of thebase station. In this case, the beam configuration information includesconfiguration information indicating one or more beam sets (e.g., atleast one of a first beam set or a second beam set) of the plurality oftransmission beams. For example, the beam configuration information maymean configuration information on the above-described beam set (orcandidate beam set). A method of configuring and method of forwardingthe beam configuration information have been described above.

For example, the one or more beam sets (e.g., the first beam set and thesecond beam set) may be configured in different resource regions inwhich a downlink control channel may be transmitted (e.g., FIG. 12). Inthis case, at least one of a time resource or a frequency resource maybe differently configured for each resource region configured for theone or more beam sets. That is, at least one of a time resource or afrequency resource may be differently configured in the resource regionconfigured in the first beam set compared to the resource regionconfigured in the second beam set.

Furthermore, the size of the one or more beam sets may be determinedbased on a time unit in which downlink control information of a specificphysical channel may be transmitted. Furthermore, the scheduling of theresource region configured in each of the one or more beam sets may beperformed in a specific resource block unit.

After the terminal receives the beam configuration information, at stepS1310, the terminal receives, from the base station, beam indicationinformation indicating (or representing) at least one of the pluralityof transmission beams of the base station. In this case, the beamindication information may mean information indicating (or representing)a specific beam set(s) of the above-described candidate beam sets (orinformation indicating (or representing) a specific beam within aspecific beam set).

Thereafter, at step S1315, the terminal receives a downlink controlchannel through a specific transmission beam. In this case, the specificbeam may mean a specific beam identified among the at least onetransmission beam based on the beam configuration information and thebeam indication information. In this case, the specific beam may beindicated through a specific preamble or a specific physical channelreceived in a symbol prior to a symbol in which the downlink controlchannel is received.

Furthermore, in various embodiments of the present invention, the beamconfiguration information and the beam indication information may bereceived through higher layer signaling as described above. Furthermore,the beam configuration information may be received through a radioresource control message, and the beam indication information may bereceived through a medium access control (MAC) control element (CE).Furthermore, the beam configuration information may be received throughhigher layer signaling, and the beam configuration information may bereceived through higher layer signaling.

Furthermore, in various embodiments of the present invention, a terminalmay perform beam measurement on a plurality of transmission beams of thebase station, and may report, to a base station, information for one ormore of the plurality of transmission beams. In this case, theinformation for the one or more transmission beams may further includeinformation for one or more reception beams of the terminal,corresponding to the one or more transmission beams. In this case, thereporting operation may be performed prior to the operation of receivingthe beam indication information.

Overview of Device to which the Present Invention May be Applied

FIG. 14 illustrates a block diagram of a wireless communication deviceto which methods proposed in this specification may be applied.

Referring to FIG. 14, a wireless communication system includes an eNB1410 and a plurality of UEs 1420 disposed within the area of the eNB1410.

The eNB 1410 includes a processor 1411, memory 1412 and a radiofrequency (RF) unit 1413. The processor 1411 implements the functions,processes and/or methods proposed in FIGS. 1 to 13. The layers of aradio interface protocol may be implemented by the processor 1411. Thememory 1412 is connected to the processor 1411 and stores a variety ofpieces of information for driving the processor 1411. The RF unit 1413is connected to the processor 1411 and transmits and/or receives radiosignals.

The UE 1420 includes a processor 1421, memory 1422 and an RF unit 1423.

The processor 1421 implements the functions, processes and/or methodsproposed in FIGS. 1 to 13. The layers of a radio interface protocol maybe implemented by the processor 1421. The memory 1422 is connected tothe processor 1421 and stores a variety of pieces of information fordriving the processor 1421. The RF unit 1423 is connected to theprocessor 1421 and transmits and/or receives radio signals.

The memory 1412, 1422 may be positioned inside or outside the processor1411, 1421 and may be connected to the processor 1411, 1421 by variouswell-known means.

For example, in a wireless communication system supporting low latencyservice, in order to transmit and receive downlink (DL) data, a UE mayinclude a radio frequency (RF) unit for transmitting and receiving radiosignals; and a processor functionally connected to the RF unit.

Furthermore, the eNB 1410 and/or the UE 1420 may have a single antennaor multiple antennas.

The aforementioned embodiments are achieved by a combination ofstructural elements and features of the present disclosure in apredetermined manner. Each of the structural elements or features shouldbe considered selectively unless specified separately. Each of thestructural elements or features may be carried out without beingcombined with other structural elements or features. In addition, somestructural elements and/or features may be combined with one another toconstitute the embodiments of the present disclosure. The order ofoperations described in the embodiments of the present disclosure may bechanged. Some structural elements or features of one embodiment may beincluded in another embodiment, or may be replaced with correspondingstructural elements or features of another embodiment. Moreover, it isapparent that some claims referring to specific claims may be combinedwith another claims referring to the other claims other than thespecific claims to constitute the embodiment or add new claims by meansof amendment after the application is filed.

The embodiments of the present disclosure may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present disclosure may be achieved by one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentdisclosure may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in the memory and executed bythe processor. The memory may be located at the interior or exterior ofthe processor and may transmit data to and receive data from theprocessor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the inventions. Thus, itis intended that the present disclosure covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

A method for receiving a downlink channel in a wireless communicationsystem of the present invention has been described based on an examplein which the method is applied to the 3GPP LTE/LTE-A system and a 5Gsystem (new RAT system), but may be applied to various wirelesscommunication systems in addition to the 3GPP LTE/LTE-A system and the5G system.

What is claimed is:
 1. A method of receiving, by a terminal, a physicaldownlink control channel (PDCCH) in a wireless communication system, themethod comprising: receiving, from a base station (BS), configurationinformation related to a plurality of beams through a Radio ResourceControl (RRC) signaling, wherein the plurality of beams are configuredfor each resource region for monitoring the PDCCH; receiving, from theBS, beam information through a physical channel, the beam informationrelated to a specific beam among the plurality of beams, and receivingthe PDCCH through the specific beam in a resource region.
 2. The methodof claim 1, wherein the monitoring the PDCCH in the resource regioncomprises performing blind decoding for the PDCCH in the resourceregion.
 3. The method of claim 1, wherein the resource region isconfigured as at least one of a time resource and/or a frequencyresource.
 4. The method of claim 1, wherein the specific beam isindicated through a specific preamble or a specific physical channelreceived in a symbol prior to a symbol in which the PDCCH is received.5. The method of claim 1, further comprising: reporting, to the BS,information for one or more beams of the plurality of beams, byperforming beam measurement on the plurality of beams.
 6. The method ofclaim 5, wherein the information for the one or more beams furthercomprises information for one or more reception beams of the terminalcorresponding to the one or more beams.
 7. The method of claim 1,wherein the configuration information and the beam information arereceived through higher layer signaling.
 8. The method of claim 1,wherein the beam information is received through a medium accesscontrol-control element (MAC-CE).
 9. The method of claim 1, wherein abit size for the plurality of beams is determined based on a time unitin which downlink control information of the PDCCH is capable of beingtransmitted.
 10. The method of claim 1, wherein the resource region isone of a plurality of resource regions related to the terminal, andwherein the plurality of resource regions is divided based on a unit ofmonitoring the PDCCH.
 11. A terminal receiving a physical downlinkcontrol channel (PDCCH) in a wireless communication system, the terminalcomprising: at least one transceiver configured to transmit and receiveradio signals, and at least one processor functionally connected to theat least one transceiver, wherein the at least one processor isconfigured to: receive, from a base station (BS), configurationinformation related to a plurality of beams for the PDCCH through aRadio Resource Control (RRC) signaling, wherein the plurality of beamsare configured for each resource region for monitoring the PDCCH,receive, from the BS, beam information through a physical channel, theinformation related to a specific beam among the plurality of beams, andreceive the PDCCH through the specific beam in a resource region. 12.The terminal of claim 11, wherein the resource region is a resourceregion monitored, by the terminal, for the PDCCH.
 13. The terminal ofclaim 11, wherein the resource region is one of a plurality of resourceregions related to the terminal, and wherein the plurality of resourceregions is divided based on a unit of monitoring the PDCCH.